The Yedikule (Seven Towers) city gate is located along the 5,632 meter-long land walls, which start at the end of the sea walls. It is one of the main entrances to the city. Over the gate, there is the double-headed eagle of Byzantium. Inside Yedikule is another imposing gate, built in 390 by Theodosius I as the arch of victory for the commanders returning home from victorious battle. It was later turned into one of the fortress gates after Theodosius II added the new city walls to the old ones. The Byzantines called this gate Porta Aurea (golden gate). After the conquest, the Turks added a new fortress which formed an independent castle and gave it the name Yedikule. The Ottoman Treasury was kept in this tower for a while, and it was turned into a prison for political prisoners in later times. Only the ruins of the minaret of the mosque which was built for the guardians can be seen today. The ruins of the amphitheater also remain.